Electron–ion coupling effects on simulations of radiation damage in pyrochlore waste forms

Abstract

We have performed molecular dynamics simulations of cascade damage in the gadolinium pyrochlore Gd₂Zr₂O₇, comparing results obtained from traditional simulation methodologies that ignore the effect of electron-ion interactions with a 'two-temperature model' in which the electronic subsystem is modeled using a diffusion equation to determine the electronic temperature. We find that the electron-ion interaction friction coefficient γ(p) is a significant parameter in determining the behavior of the system following the formation of the primary knock-on atom (PKA; here, a U³(+) ion). The mean final PKA displacement and the number of defect atoms formed is shown to decrease uniformly with increasing γ(p); however, other properties, such as the final equilibrium temperature and the oxygen-oxygen radial distribution function, show a more complicated dependence on γ(p).

Nd and Ce simultaneous substitution driven structure modifications in Gd2−xNdxZr2−yCeyO7

“…[5][6][7] As nuclear waste forms materials, structures based on titanate, stannate and zirconate pyrochlore have been investigated extensively. [8][9][10][11][12][13][14] In contrast to titanate pyrochlore which are susceptible to radiation induced amorphization, the zirconate ceramics show remarkable resistance to amorphization under ion beam irradiation. Thus Gd 2 Zr 2 O 7 has been proposed as a nuclear waste forms materials for the immobilization of americium and plutonium due to its radiation stability.…”

Electronic effects in high-energy radiation damage in iron

“…Although electronic stopping has been commonly taken into account in cascade simulations [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], there are no systematic studies that include a dynamic, location-dependent description of how the e-p coupling affects the atom dynamics in collision cascades. Examining this issue is especially important in high-energy cascades, where the electronic excitations matter most.…”

Fast analysis of molecular dynamics trajectories with graphics processing units—Radial distribution function histogramming

“…For example, Kadau and coworkers investigated shock wave induced phase transitions in metals using radial distribution functions calculated from simulations of systems with 8 million atoms [7]. Radial distribution functions calculated from systems of several hundred thousand to one million atoms have also been useful in studies of radiation damage in nuclear waste [8] and long-range order in self-assembled alkanethiol monolayers [9]. The RDF is also widely used in astrophysics, where stars replace atoms and the function is typically known as the two-point correlation function [10].…”